Asteroids vs. CometsSpacecrafts have retrieved extraordinarily valuable information that has furthered the human race’s knowledge of what exists in outer space. However, spacecrafts and shuttles are extremely expensive to build and launch into space so they should be well taken care of. Sending a spacecraft to an asteroid is far better and safer than sending a spacecraft to a comet for quite a few different reasons. First, an asteroid is made up of less materials than a comet. Next, comets produce two tails when approaching the Sun. Lastly, an asteroid’s orbit is much more predictable than a comet’s orbit. With these characteristics, asteroids make a better object for spacecrafts to land on rather than comets.

A typical asteroid is made up of rock, metal, and iron. The iron causes asteroids to be rock solid with some loose piles of rubble. Comets consist of many different materials such as ice and dust. With less exposed materials, sending a spacecraft to an asteroid instead of a comet reduces unexpected obstacles with the comet’s atmospheric conditions. Having an atmosphere with high levels of water and dust can also make the spacecraft’s maneuvering difficult. An asteroid would be much more suitable for spacecraft maneuvering due to it’s rocky and dry shell.

Comets produce two tails when they get closer to the Sun while asteroids produce no tails. These two tails consist of one white tail made of dust and another blue tail containing ionized gas. The Sun’s light creates radiation pressure and when mixed with solar wind, they push the dust and gas outward and away from the Sun thus creating the two tails. Exposing a spacecraft to these conditions can be very detrimental to the exterior and technology of the spacecraft. Which would be very counterproductive and could potentially destroy any evidence recorded. Asteroids, however, are basically big piles of rubble with craters. Spacecrafts would have a much easier time landing on an asteroid...

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...﻿ASTEROIDS
Did you know that there are really millions of planets orbiting the Sun? Apart from nine “proper” planets, there are a few million, minor ones, called asteroids. These are different chunks of rock, which range from specks of dust to those which are a few kilometres across. Most of them travel in an orbit between Mars and Jupiter called the asteroid belt. Others follow different orbits. In the 18th century, astronomers were convinced that a missing world existed between Mars and Jupiter. A search was mounted and the first asteroid, Ceres, was discovered by an Italian astronomer Giuseppe Piazzi in 1801. Today, over 5000 have been catalogued.
Most asteroids journey around the Sun in the asteroid belt. Others are in smaller groups with different orbits. A group named the Trojans travel along Jupiter’s path- some in front of the planet and some behind. A group called the Apollo family have orbits that cross the path of Earth. One remote asteroid called Chiron orbits between Saturn and Uranus. At this distance from the Sun, it is made from ice, not rock.
Astronomers can calculate an asteroid’s size by studying its brightness (how much of the Sun’s light it reflects) by timing it as it crosses a background star, or by direct measurement if it comes close to Earth. The largest asteroid, Ceres, is 933 km (580 miles) in diameter, but most are less than 100 km...

...﻿Comet-A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail.
Asteroid-Asteroids are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do. They have also been called planetoids, especially the larger ones. Asteroids are small, airless rocky worlds revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets. In total, the mass of all the asteroids is less than that of Earth's moon. But despite their size, asteroids can be dangerous. Many have hit Earth in the past, and more will crash into our planet in the future. That's one reason scientists study asteroids and are eager to learn more about their numbers, orbits and physical characteristics.
Meteor-A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor. A meteoroid is a piece of stone-like or metal-like debris which travels in outer space....

...Comets
Belinda Scott
Introduction to Physical Science – SCI 110
Dr. Paul A. Belony, Jr.
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A comet is a small body, roughly the size of a small town, in the Solar System. It is made up of ice, rock, dust, carbon dioxide, ammonia, methane and more. Some researchers think comets might have originally brought some of the water and organic molecules to Earth that now make up life here.
Comets become visible as they near the Sun. The tail of a comet is its most characteristic feature. Round and round a comet goes in its orbit and when it comes into the inner solar system. Each time a comet gets closer to the Sun, the ice on the surface of the nucleus, measuring ten miles or less, begins turning into gas, forming a cloud known as the coma. Radiation from the sun pushes dust particles away from the coma, which can reach 1 million miles wide, forming a dust tail, while charged particles from the sun convert some of the comet's gases into ions, forming a stream of volatile materials known as an ion tail. Some tails can reach 100 million miles long. The tail of the comet always points away from the Sun, since they are shaped by sunlight and the solar wind, so that when the comet is receding from the Sun, its tail actually runs before it. Typical comet loses about one tenth of a percent of its mass every...

...The first written records of comets date back to nearly 3,000 years ago from
China and Europe. The accounts of these comets were believed to be the causes of
terrible events that occurred afterwards. In more recent times, however, astronomers have
found out what they really are. A comet is basically a mixture of ices, from both
water and frozen gases, and dust. They have also been given the names "dirty snowballs" or
"icy mudballs." The typical comet is less that 10 kilometers across. They spend most of
their time frozen solid in the outer parts of our solar system. Comets are composed of five
parts: the nucleus, coma, hydrogen cloud, dust tail, and ion tail. The nucleus is
pretty solid and stable, composed mostly of ice and gas with a small amount of dust and other
solids. The surface of the nucleus is best described as a black crust. Comet nuclei can
range from 1 kilometer to about 50 kilometers across. The black crust on the surface of
the nuclei helps the comet to absorb heat, which causes some of the ices under the crust to
turn to a gas. Pressure builds up underneath the crust and causes the surface to bubble up
in some places. Eventually, the weak spots of the crust break open from the pressure, and the gas
shoots outward; this is referred to by astronomers as a jet. Dust that had
been mixed in with the gas is also pushed...

...
An asteroid is a minor planet in the inner solar system, the term minor planet has historically been applies to any astronomical object orbiting the sun that did not show the disk of a planet. Asteroids supposedly don’t have the characteristics of an active comet but their volatile based surfaces resemble comets more closely than originally thought.(1) Whereas a meteorite is a small rocky or metallic body that travels through space, they are significantly smaller than asteroids and range in size from small grains to 1 meter-wide objects. Smaller objects than this are classified as micrometeoroids or space dust; most of these are fragments from comets or asteroids after a collision.(2) An impact crater is a hole excavated out of a surface usually circular (e.g. a planet, moon, asteroid, or comet) when a smaller mass moving at very high speed collides with it. Impact craters typically have raised rims and floors that are lower in elevation than the surroundings. Meteor crater is perhaps the best-known example of a small impact crater on the Earth. (3) The Barringer crater is over a kilometre in diameter and 750ft in depth.(4) The size and shape of the crater depends on factors such as the velocity and mass of the impacter and the surface it hits. The faster the incoming impacter, the larger the crater. (5) Because of physics the total amount of...

...tells about how comets are important and their effect on earth and its people.<br><br>Comets are leftover scrubs of material that did not make it to planethood in the events creating our solar system. They orbit in a perpetual Deepfreeze until some subtle gravitational nudge upsets the delicate balance. The Great Falls begins. First a snowball drifts towards the sun and steadily accelerates. As solar radiation heats the comets the ice within sublimates, escaping as gas from vents from the surface. Sometimes jets of sublimating ice whirl off the rotating comet nucleus like a firework pinwheel. Dust trapped in the ice breaks free. Pushed back by the pressure of the sun's radiation, the dust streams out behind the comet in what appears as a fairytale. The comet is among the fastest thing in the solar system.<br><br>The most important new results are that the comet contains carbon compounds with trace of nitrogen sodium and sulfur. These ingredients are essential for life on earth. That is why scientist believes that a comet might have crushed on earth and from that moment life began. The ion tales are believed to be a kind of wind sock for the solar wind and NASA scientists are hoping to use it to get weather reports from distant solar system.<br><br>Most comets can be only seen with a telescope but every once in a while an impressive one is visible to...

...Halley’s Comet
Astronomers first observed Halley’s Comet as far back as 200 BCE. The comet's periodicity was first determined in 1705 by English astronomer Edmond Halley, who it was eventually named after. Halley's Comet last appeared in the inner Solar System in 1986 and won’t appear again until mid-2061. Although the nucleus of the comet itself is not that large, the coma can extend to a very large size.
As the gas molecules in the coma are ionized by the solar ultraviolet radiation pressure from the solar wind, a stream of particles emitted by the Sun, pulls the coma's ions out into a long tail, which may extend more than 100 million kilometers into space. The nucleus itself is only 15 kilometers long, 8 kilometers wide and 8 kilometers thick. In comparison, the earth has a diameter of 12,756 km and the sun has a diameter of 1,392,000 km. This means that Halley’s Comet is only about 4% the size of earth but because of it’s coma, it appears much larger to the naked eye. While the planets orbit around the sun, Halley’s Comet orbits towards and away from the sun, all the way out to Jupiter, perpendicular to the planet’s orbits.
Halley is classified as a periodic or short-period comet, one with an orbit lasting 200 years or less. This contrasts it with long-period comets, whose orbits last for thousands of years. Most short-period comets,...

...Movement of
CometsComets...Dirty Ball of Ice
• They look like a star with
a ghostly white tail.
• The term comet derived
from the Greek word
“aster kometes”, which
means long-haired star.
• Composed of ice, frozen
gases (ammonia,
methane, Carbon
dioxide, and other
organic compounds.
Comets…where they come from?
Kuiper Belt -
Similar
to asteroid but found
beyond Neptune.
Oort Cloud – Discovered
in 1950 by Jan Oort,
found beyond Pluto.
Movement of Comets
•
The red circle represents
the orbit of one planet.
Although the comet in the
animation is orbiting (blue)
the Sun in a counter
clockwise direction, there
are many comets that orbit
in the opposite direction.
As can be seen from the
diagram, the tail of the
comet always point away
from the Sun, so after a
comet has passed the Sun
it actually travels tail first.
Movement of Comets
• They travel around the sun in long looping
orbits that bring them near the sun on one
end and around Jupiter on the other hand.
• If a comet has large orbit, it takes a long
time to go around the sun. Some are
“short-period” comets that take 5 or 10
years to complete an orbit. Some are
“long-period” comets that take decades,
centuries, or millennia to orbit the sun.
Movement of Comets…example
Comets…...